As if this wasn't already a large number, the $21 trillion is held by 100 million people, while $9.8 trillion is held by just 100,000 people.

For those keeping score at home, that means on average these 100,000 people tucked away about $98 million in offshore accounts.

"Since most of the missing financial wealth belongs to a tiny elite, the impact is staggering," says Henry. "For most countries, global financial inequality is not only much greater than we suspected, but it has been growing much faster."

Had this money been taxed as income, Henry estimates it could have brought in around $190 to $280 billion. That doesn't even include revenues from estate, capital gains or other types of taxes.

With this much money being left on the table, it makes sense the government would want these tax cheats to pay up. One program seems to offer a solution. Recently the tax man has given tax cheats a limited time to fess up and pay taxes without any penalties, and so far the U.S. has collected over $5 billion of tax revenues it may never have gotten its hands on otherwise.